Additive effect of atropine eye drops and short-term retinal defocus on choroidal thickness in children with myopia.

Atropine eye drops and myopic retinal defocus each slow progression of myopia (short-sight). They also cause thickening of the choroid, and it has been suggested that the thickening is a precursor for reduced eye growth and slowed myopia progression. We investigated whether choroidal thickening due to optical defocus would add to thickening due to atropine when both were applied simultaneously. Addition would suggest that combining the two clinical treatments may improve efficacy of myopia control. We studied 20 children receiving 0.3% atropine daily for myopia control, over a period of 6 months. We imposed short periods of retinal defocus (1 h of myopic or hyperopic defocus (± 2.00D)) both before, and after 1 week and 3 and 6 months of atropine treatment. Prior to atropine, myopic or hyperopic defocus caused significantly thicker or thinner choroids respectively (± 12 µm, p < 0.001). After one week of atropine alone, thickness had increased (+ 21 µm; SD 17 µm; p < 0.001), and it increased further (by + 13 µm; SD 6 µm; p < 0.001) when exposed to myopic defocus. Atropine abolished choroidal thinning in response to hyperopic defocus. These effects remained the same after 3 and 6 months of atropine treatment. Our results show that additive effects of atropine and optical defocus are present at the level of the choroid, and suggest that combining optical and pharmaceutical treatments is likely to enhance efficacy of clinical myopia control.

Effect of Optical Defocus on Choroidal Thickness in Healthy Adults With Presbyopia.

Purpose: To investigate changes in subfoveal choroidal thickness (SFCT) induced by retinal defocus in presbyopic adults. Methods: Thirty-seven healthy presbyopic subjects (age 57.74 ± 4.06 years) with low refractive errors (+0.08 ± 1.09 Diopters [D]) viewed a distant target (video movie at 6 m) for 60 minutes on two occasions while SFCT was monitored with optical coherence tomography every 20 minutes. On each occasion, both eyes were optimally corrected for distance: one eye acted as control, while the other (experimental) eye viewed through an additional ophthalmic lens: a +2.00 D lens imposing myopic defocus on one occasion and a -2.00 D lens imposing hyperopic defocus on the other occasion. Results: Baseline SFCT was not different between experimental and control eyes (226 ± 72 µm vs. 232 ± 75 µm; P = 0.28). Myopic defocus caused a significant (P < 0.001) increase in SFCT in the defocused eye by 20 minutes (and +10 ± 5-µm increase at 60 minutes: P < 0.001), while hyperopic defocus caused a significant decrease in SFCT by 20 minutes (and -10 ± 5-µm decrease at 60 minutes: P < 0.001) with no change in control eyes. Conclusions: In presbyopic subjects, imposed myopic retinal defocus caused thickening of SFCT, while hyperopic defocus caused thinning of SFCT. This implies that uncorrected presbyopia, which is associated with hyperopic retinal defocus for near objects and which is highly prevalent in the developing world, would likely be associated with choroidal thinning and possibly reduced choroidal blood flow with prolonged periods in a near visual environment.

Effect of Atropine Eye Drops on Choroidal Thinning Induced by Hyperopic Retinal Defocus.

PURPOSE: To investigate the effects of atropine on choroidal thinning induced by hyperopic retinal defocus. METHODS: Ten young adults with myopia (-1.00 D to -5.00 D) viewed a video at 6 metres for 60 minutes on successive days. On day 1, one eye (control) was distance corrected with a contact lens; the other (experimental) eye wore a contact lens imposing 2.00 D of hyperopic retinal defocus. Sub- and perifoveal choroidal thickness (SFCT, PFCT) were monitored with optical coherence tomography. On day 2, the procedure was repeated but the experimental eye had received one drop of 0.5% atropine 22 hours earlier. RESULTS: On day 1, eyes exposed to hyperopic defocus developed progressively thinner choroids (SFCT (baseline) = 253 ± 32 µm versus SFCT (40 mins) = 244 ± 31 µm, p = 0.004), whereas SFCT and PFCT in control eyes did not change (p > 0.17). On day 2 (22 hours after instilling atropine), baseline SFCT and PFCT were not different to day 1 (p > 0.05) and hyperopic defocus failed to thin the choroid (max change in SFCT = +2 ± 2 µm, p = 0.36). CONCLUSIONS: Atropine abolished choroidal thinning induced by hyperopic defocus without changing baseline choroidal thickness. The results suggest that atropine inhibits signals associated with hyperopic defocus, for example, from lag of accommodation during near work. This trial is registered with ACTRN12617001519347.

Effect of retinal image defocus on the thickness of the human choroid.

PURPOSE: To describe the time-course and amplitude of changes to sub-foveal choroidal thickness (SFCT) induced by imposed hyperopic and myopic retinal defocus and to compare the responses in emmetropic and myopic subjects. METHODS: Twelve East Asian subjects (age: 18-34 years; six were emmetropic and six had myopia between -2.00 and -5.00 dioptres (D)) viewed a distant target (video movie at 6 m) for 60 min on two separate occasions while optical coherence tomography (OCT) images of the choroid were taken in both eyes every 5 min to monitor SFCT. On each occasion, one eye was optimally corrected for distance with a contact lens while the other eye wore a contact lens imposing either 2.00 D hyperopic or 2.00 D myopic retinal defocus. RESULTS: Baseline SFCT in myopic eyes (mean ± S.D.): 256 ± 42 µm was significantly less than in emmetropic eyes (423 ± 62 µm; p < 0.01) and was correlated with magnitude of myopia (-39 µm per dioptre of myopia, R(2) = 0.67: p < 0.01). Repeated measures anova (General Linear Model) analysis revealed that in both subject groups, 2.00 D of myopic defocus caused a rapid increase in SFCT in the defocussed eye (significant by 10 min, increasing to approximately 20 µm within 60 min: p < 0.01), with little change in the control eye. In contrast, 2.00 D of hyperopic defocus caused a decrease in SFCT in the experimental eye (significant by 20-35 min. SFCT decreased by approximately 20 µm within 60 min: p < 0.01) with little change in the control eye. CONCLUSIONS: Small but significant changes in SFCT (5-8%) were caused by retinal defocus. SFCT increased within 10 min of exposure to 2.00 D of monocular myopic defocus, but decreased more slowly in response to 2.00 D of monocular hyperopic defocus. In our relatively small sample we could detect no difference in the magnitude of changes to SFCT caused by defocus in myopic eyes compared to emmetropic eyes.